1. Technical Field
The present disclosure relates to a dissimilar material joining structure and a producing method of a dissimilar material joined body.
2. Description of Related Art
There have been known techniques of joining dissimilar materials to each other (see Japanese Patent Application Publication No. 2013-22622, Japanese Patent Application Publication No. 2013-133044, and Japanese Patent Application Publication No. 2005-308116). For example, the following JP 2013-22622 A discloses a technique of joining a steel member and an aluminum alloy member using a steel piercing metal. Specifically, this piercing metal integrally includes a columnar shaft and a head in a disk shape having a greater diameter than that of the shaft and located at a first end of the shaft in an axial direction of the shaft. The shaft of this piercing metal is hammered into the aluminum alloy member so that the shaft forms a through-hole in the aluminum alloy member, and the head comes into contact with a surface of the aluminum alloy member. After the piercing metal hammered in this manner is clamped, a front end of the shaft of the piercing metal and the steel member are joined through spot-welding, thereby joining the steel member and the aluminum alloy member to each other via the piercing metal.
In this related art, the aluminum alloy member is punched by the columnar shaft of the piercing metal during the above production, thereby producing a structure in which an outer circumferential surface of the shaft of the piercing metal is in contact with an inner circumferential surface of the through-hole of the aluminum alloy member. Hence, during heating in a coating-drying process or the like, for example, if a difference in elongation occurs between the steel member and the aluminum alloy member due to a difference in linear expansion therebetween, a load is applied to the shaft of the piercing metal and the through-hole of the aluminum alloy member. However, the difference in linear expansion between the steel member and the aluminum alloy member during heating is relatively small, so that a preferable joint condition between the steel member and the aluminum alloy member is maintained.
The joining-targets in the related art described in the above JP 2013-22622 A are both metallic members, but there are demands to join metallic members and resin members in light of reduction in weight. However, a difference in linear expansion between metallic members and resin members during heating is often greater than a difference in linear expansion between dissimilar metallic members during heating. Hence, in a structure of joining a metallic member and a resin member using a piercing metal (rivet) in a shape as described in the above related art, there is room for improvement of maintaining a preferable joint condition between the metallic member and the resin member during heating.